1. Field of the Invention
This invention relates to an intraocular pressure monitoring device, more particularly to a wireless intraocular pressure monitoring device.
2. Description of the Related Art
Glaucoma, one of the eye diseases that lead to vision loss, may be categorized into chronic simple glaucoma and acute congestive glaucoma. Chronic simple glaucoma, also known as open-angle glaucoma, accounts for approximately 90% of the cases in the U.S., is characterized by a gradual rise in intraocular pressure, and does not cause pain. On the other hand, acute congestive glaucoma, also known as narrow-angle glaucoma, is less common and is characterized by a sudden rise in intraocular pressure generally attributed to blockage of the drainage route of the aqueous humor. Symptoms associated with this type of glaucoma may be alleviated by using certain types of eye drops to improve drainage of the aqueous humor and/or using certain drugs (e.g., diuretics) to suppress secretion of the aqueous humor.
According to the statistics of the World Health Organization (WHO), there are approximately 67 million cases of glaucoma worldwide, among which 6.4 million cases progressed to complete vision loss. Moreover, the elderly accounts for 75% of the 6.4 million cases. The statistics further show that, among the population of age 40 or above (currently 3 million people), 0.12 million people suffered vision loss due to glaucoma.
Currently, glaucoma cannot be cured, and symptoms and development of which can only be suppressed through the use of drugs and/or through surgical operations, which aim to reduce the intraocular pressure so as to prevent damage to the optic nerves. Relevant researches further indicate that the main cause of glaucoma has been the variation in intraocular pressure, and that people who are diagnosed with diabetes, who have high blood pressure or myopia, and who have family members suffering from glaucoma are at high risk of developing glaucoma.
Therefore, timely control of intraocular pressure is the most important part of controlling the development of glaucoma. That is to say, regular monitoring of intraocular pressure is important, especially in finding out the cause of a rise in the intraocular pressure of a patient. However, since access to relevant medical equipments is generally limited due to their prices and sizes, people with glaucoma are generally unaware of their own biological statuses.
Referring to FIG. 1, U.S. Pat. No. 7,137,952 discloses a conventional non-invasive wireless intraocular pressure monitoring device including a sensor unit 1, an interrogation unit 14, a wireless receiver unit 15, and a computer device 16.
The sensor unit 1 includes a soft contact lens 101 made of silicone, an active resistive strain gauge 10, a passive resistive strain gauge 11, a low-power transponder 12, and an antenna 13. The active and passive resistive strain gauges 10, 11 are arranged to form a Wheatstone bridge structure and are embedded in the soft contact lens 101. The active resistive strain gauge 10 has a resistance that varies based on a variation in curvature of the soft contact lens 101, which may be caused by a change in curvature of the cornea attributed to a change in the intraocular pressure. The passive resistive strain gauge 11, on the other hand, is operable to provide a temperature-based compensation for correcting errors associated with the variation in the resistance. Next, the resistance may be converted into a sensor voltage corresponding to the intraocular pressure.
The low-power transponder 12 is connected electrically to the Wheatstone bridge structure, and is operable to perform a first modulation process upon the sensor voltage so as to generate a first carrier-frequency signal for wireless transmission to the interrogation unit 14 via the antenna 13.
The interrogation unit 14 is operable to wirelessly power the low-power transponder 12, to wirelessly receive the first carrier-frequency signal from the low-power transponder 12, and to perform a first demodulation process upon the first carrier-frequency signal received thereby so as to obtain a demodulated voltage corresponding to the sensor voltage. The interrogation unit 14 is further operable to perform an analog-to-digital conversion process upon the demodulated voltage so as to obtain a digital signal corresponding to the sensor voltage, and to subsequently perform a second modulation process upon the digital signal so as to obtain a second carrier-frequency signal for wireless transmission to the wireless receiver unit via an antenna.
The wireless receiver unit 15 is operable to wirelessly receive the second carrier-frequency signal from the interrogation unit 14, and to perform a second demodulation process upon the second carrier-frequency signal received thereby so as to obtain demodulated data corresponding to the sensor voltage.
The computer device 16 is connected electrically to the wireless receiver unit 15 for receiving the demodulated data therefrom, and is operable to output an intraocular pressure value based on the demodulated data with reference to a conversion table that defines a plurality of relationships between a plurality of data values and a plurality of corresponding intraocular pressure values, respectively.
However, the sensor unit 1 of the conventional intraocular pressure monitoring device includes many components such that a relatively complicated and expansive manufacturing process is needed for producing the sensor unit 1 with a complex structure. Therefore, there is a need in the art to provide an intraocular pressure monitoring device that requires a relatively simple manufacturing process and that incurs a relatively low production cost.